Volvo 850 brake shudder/noise

[buster850]

Hi crew,
I have a 94 850 GLE 2.4 auto sedan.
The issue is that under normal braking conditions on flat or gentle sloped to moderate sloped roads no issues, however once cresting a steep hill and beginning to decend after about three brake applications the entire car is engulfed in the worst shudder accompanied by a loud grumbling noise, this will continue until the decent has finished upon every brake application. ( seems a common thread online)
Once the brakes have cooled off a little on the flat ground there is no more issue.
I have read many posts on the net which say this can be a few things but commonly a stuck rear caliper piston and also that the installation of "half shims" fixes the problem immediately.
I live in Australia where mechanics don't speak volvo, even volvo mechanics scratched their heads when I mentioned "half shims", generally they just were not interested in talking about the issue and couldnt wait to get off the phone so they could go back to their beer.
I need a part number for the half shims, I have a part number for the full shims which is 1359772 but cant find the half shim part number of if they are even available here in Australia.
Also are the half shims literally half the length of the brake pad or is it a full length shim with a tapering thickness over the shims length.
I will strip down the calipers tomorrow and check that the pistons are all functioning and reinstal but I am very interested in understanding more about the half shim fix.
Many thanks to any member/s who respond to this post. Cheers Buster850

[GrumpyOldMan]

Sorry I don't know the part numbers, but as a cheap fix if you have the full shim, why not just 'trim' them to suit ?
For what it's worth my '96 850 has half shims.
No idea if they were there from manufacture, but they were there when I bought the car second hand.

Try the usual suspects.
IPD, Tasca, Pelican, FCP, etc etc....

https://blog.fcpeuro.com/your-volvos-vi ... bably-fine

https://www.pelicanparts.com/More_Info/ ... rter=brand